1. Field of the Invention
Implementations of various techniques described herein generally relate to marine seismic exploration. More specifically, they relate to attenuating out of band energy emitted from marine seismic sources.
2. Description of the Related Art
The following descriptions and examples do not constitute an admission as prior art by virtue of their inclusion within this section.
Seismic sources, such as airguns, generate a pressure signal used in marine seismic exploration. Airguns can be described as having a chamber filled with a compressed gas that is released to the surrounding water through port(s). Each port is a conduit through which the compressed gas escapes the chamber and enters the surrounding water, thereby creating an acoustic pulse.
Prior art airguns emit significant acoustic pulses that have high amplitudes, forming high frequency acoustic energy. High frequency acoustic energy typically includes energy at frequencies that are of no use for imaging and are outside the frequency range of interest for seismic exploration. This out of band signal is considered noise, and may also adversely affect marine life.
Accordingly, there is a need to find ways for reducing amplitudes of the out of band frequencies emitted by seismic sources such as airguns.